18 replies to this topic

[greensilver mini]

hi on my 1275 when i start the engine up the oil light takes while to go off is this a bad thing?

Stuart

[cobblers]

How long is a while? It's generally not a good thing, but could be the switch.

What oil are you using? How long since it's been changed?

[djshongo]

mine used to be like this til i changed oil, now goes off after about 3-4secs

[Dan]

If it's using a standard 7psi oil pressure switch then it's a very bad sign. If it's using a higher pressure switch it's not so bad but still a sign of a tired engine. What oil are you using? Does the lamp turn off if you blip the throttle lightly? Does it come back on at hot idle? How soon after switching off does the lamp light up (flick the ignition off and straight back on again once the engine has stopped but don't re-start it)?

[Dan]

3 to 4 seconds is far too long! My car uses a 21psi switch and gets to that pressure within perhaps 1/2 a second of turning the key.

[greensilver mini]

im useing 20/50 oil it goes off quicker when you start it up on choke... about 20 secs it stays on but revs help it go quicker?

[Dan]

20 seconds to get to 7 psi on 20w50? You'll be rebuilding that engine soon. It's very tired.

[greensilver mini]

yeah but the engine wouldnt run that well if it tired engine?

[Stevie W]

Before condemning the engine, its worth changing the actual oil pressure switch as these can partially fail causing a flickering oil pressure light at tickover or make the light slow to go out especially if the oil is thin/hot.

If a new switch doesn't do the trick and the engine generally sounds healthy and isn't noisy (knocking etc), it could be a tired oil pump. If this is the case then the pump should be changed as soon as possible to prevent engine damage in the future.

Steve.

[greensilver mini]

iv only put this engine in and it was siting around for a year iv cleaned it up and that new head gasket changed the oil but the old oil was really black and crapy

[cobblers]

As a rough idea, my freshly rebuilt 1330 hits 45psi after about 5-10 revolutions, climbing to approx 100psi as soon as the engine starts. This falls to about 60psi on hot idle after about a dozen miles.
Perhaps invest in an oil pressure gauge/ new switch and change the oil, but if it is genuinely at >7psi for 20 seconds something is definitely amiss.
I'd be tempted to turn the engine over with the switch removed. This will fire oil out of the front of the engine but will both help you see the volume of oil being pumped, and also would clear any blockages to the switch itself. Make sure you remove the king lead from the coil to prevent the car starting and potentially running with no oil pressure at all!
Also might be worth checking the pressure regulating plunger isn't stuck, especially if the engine has been stood for some time.

I'd suspect the oil pump/plunger - Before I rebuilt my engine, it ran with a span bearing and still managed to get 20psi with oil firing all over the place.

You can probably change the pump with the engine in the car - You'd need to remove the clutch cover, flywheel and the drop gear housing to get at it, but they are only a ~ £20 part.

Edited by cobblers, 07 December 2009 - 03:50 PM.

[Guess-Works.com]

60 psi @ hot idle is way too much pressure, and I'm surprised you've not blown the oil filter off reaching 100psi...

[cobblers]

60 psi @ hot idle is way too much pressure, and I'm surprised you've not blown the oil filter off reaching 100psi...

I suspect the guage might be reading high, as it sits at about 10psi with the engine off. It's coming out again tomorrow anyway to investigate an intermittent clattering noise from the timing gear.
This is with a new minispares pressure relief ball bearing. I reused the old spring without cutting the usual 1.25 coils off because it was that much shorter than a new spring to start with.

I'll probably just replace it with the 1380 I've just bought, as I suspect there is a blocked oilway or something equally amiss with it.

Edit: Halfords 20w50, new +10 crank, mains and big ends and a new "high flow" oil pump

Edited by cobblers, 07 December 2009 - 04:28 PM.

[welshdan]

60 psi @ hot idle is way too much pressure, and I'm surprised you've not blown the oil filter off reaching 100psi...

what shopuld oil pressure be running at ideally? i rebuilt my mpi engine, it runs around 80 psi when cold/at revs, but drops to 50 psi when warm at idle

my brother had fitted a restrictor to his (restricts at 60 psi), i see the point - not to get too high a pressure, though as the revs rise surely a higher oil pressure is needed to suply oil to all of the components that need it?

[Guess-Works.com]

Think of oil like blood, high blood pressure is as bad as low blood pressure...